Environmental system including a transport region for an immersion lithography apparatus

ABSTRACT

A lithographic projection apparatus that is arranged to project a pattern from a patterning device onto a substrate using a projection system has a liquid supply system arranged to supply a liquid to a space between the projection system and the substrate. The apparatus also includes a liquid removal system having a conduit having an open end adjacent a volume in which liquid will be present, a porous member between the end of the conduit and the volume, and a suction device arranged to create a pressure differential across the porous member.

RELATED APPLICATIONS

This is a Divisional of U.S. patent application Ser. No. 11/236,713filed Sep. 28, 2005 (now U.S. Pat. No. 7,251,017), which is aContinuation of International Application No. PCT/US2004/009994 filedApr. 1, 2004, which claims the benefit of U.S. Provisional PatentApplication No. 60/462,112 filed on Apr. 10, 2003 and U.S. ProvisionalPatent Application No. 60/485,033 filed on Jul. 2, 2003. The disclosuresof these applications are incorporated herein by reference in theirentireties.

BACKGROUND

Exposure apparatus are commonly used to transfer images from a reticleonto a semiconductor wafer during semiconductor processing. A typicalexposure apparatus includes an illumination source, a reticle stageassembly that positions a reticle, an optical assembly, a wafer stageassembly that positions a semiconductor wafer, and a measurement systemthat precisely monitors the position of the reticle and the wafer.

Immersion lithography systems utilize a layer of immersion fluid thatfills a gap between the optical assembly and the wafer. The wafer ismoved rapidly in a typical lithography system and it would be expectedto carry the immersion fluid away from the gap. This immersion fluidthat escapes from the gap can interfere with the operation of othercomponents of the lithography system. For example, the immersion fluidcan interfere with the measurement system that monitors the position ofthe wafer.

SUMMARY

The invention is directed to an environmental system for controlling anenvironment in a gap between an optical assembly and a device that isretained by a device stage. The environmental system includes animmersion fluid source and a transport region that is positioned nearthe device. The immersion fluid source delivers an immersion fluid thatenters the gap. The transport region captures immersion fluid that isexiting the gap. With this design, in certain embodiments, the inventionavoids the use of direct vacuum suction on the device that couldpotentially distort the device and/or the optical assembly.

In one embodiment, the environmental system includes a fluid barrierthat is positioned near the device and that encircles the gap.Furthermore, the fluid barrier can maintain the transport region nearthe device.

In one embodiment, the environmental system includes a fluid removalsystem that removes immersion fluid from near the transport region. Inanother embodiment, the fluid removal system can direct a removal fluidthat removes immersion fluid from the transport region. In thisembodiment, the removal fluid can be at a removal fluid temperature thatis higher than an immersion fluid temperature of the immersion fluid.

In one embodiment, the transport region is a substrate that includes aplurality of passages for collecting the immersion fluid near thetransport region. As an example, the transport region can be made of amaterial that conveys the immersion fluid by capillary action. In thisembodiment, the passages can be a plurality of pores. In an alternativeembodiment, the passages can be a plurality of spaced apart transportapertures that extend through the transport region.

The present invention also is directed to an exposure apparatus, awafer, a device, a method for controlling an environment in a gap, amethod for making an exposure apparatus, a method for making a device,and a method for manufacturing a wafer.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described in conjunction with exemplaryembodiments in which like reference numerals designate like elements,and in which:

FIG. 1 is a side illustration of an exposure apparatus having featuresof the invention;

FIG. 2A is a perspective view of a portion of the exposure apparatus ofFIG. 1;

FIG. 2B is a cut-away view taken on line 2B-2B of FIG. 2A;

FIG. 2C is an enlarged detailed view taken on line 2C-2C in FIG. 2B;

FIG. 2D is an enlarged detailed view of another embodiment of a portionof an exposure apparatus;

FIG. 3A is a side illustration of an immersion fluid source havingfeatures of the invention;

FIG. 3B is a side illustration of a fluid removal system having featuresof the invention;

FIG. 3C is a side illustration of another embodiment of a fluid removalsystem having features of the invention;

FIG. 3D is a side illustration of another embodiment of a fluid removalsystem having features of the invention;

FIG. 4 is an enlarged cut-away view of a portion of another embodimentof an exposure apparatus;

FIG. 5A is an enlarged cut-away view of a portion of another embodimentof an exposure apparatus;

FIG. 5B is an enlarged detailed view taken on line 5B-5B in FIG. 5A;

FIG. 6A is a flow chart that outlines a process for manufacturing adevice in accordance with the invention; and

FIG. 6B is a flow chart that outlines device processing in more detail.

DETAILED DESCRIPTION OF EMBODIMENTS

FIG. 1 is a schematic illustration of a precision assembly, namely anexposure apparatus 10 having features of the invention. The exposureapparatus 10 includes an apparatus frame 12, an illumination system 14(irradiation apparatus), an optical assembly 16, a reticle stageassembly 18, a device stage assembly 20, a measurement system 22, acontrol system 24, and a fluid environmental system 26. The design ofthe components of the exposure apparatus 10 can be varied to suit thedesign requirements of the exposure apparatus 10.

A number of Figures include an orientation system that illustrates an Xaxis, a Y axis that is orthogonal to the X axis, and a Z axis that isorthogonal to the X and Y axes. It should be noted that these axes alsocan be referred to as the first, second and third axes.

The exposure apparatus 10 is particularly useful as a lithographicdevice that transfers a pattern (not shown) of an integrated circuitfrom a reticle 28 onto a semiconductor wafer 30 (illustrated inphantom). The wafer 30 is also referred to generally as a device, orwork piece. The exposure apparatus 10 mounts to a mounting base 32,e.g., the ground, a base, or floor or some other supporting structure.

There are a number of different types of lithographic devices. Forexample, the exposure apparatus 10 can be used as a scanning typephotolithography system that exposes the pattern from the reticle 28onto the wafer 30 with the reticle 28 and the wafer 30 movingsynchronously. In a scanning type lithographic apparatus, the reticle 28is moved perpendicularly to an optical axis of the optical assembly 16by the reticle stage assembly 18 and the wafer 30 is movedperpendicularly to the optical axis of the optical assembly 16 by thewafer stage assembly 20. Irradiation of the reticle 28 and exposure ofthe wafer 30 occur while the reticle 28 and the wafer 30 are movingsynchronously.

Alternatively, the exposure apparatus 10 can be a step-and-repeat typephotolithography system that exposes the reticle 28 while the reticle 28and the wafer 30 are stationary. In the step and repeat process, thewafer 30 is in a constant position relative to the reticle 28 and theoptical assembly 16 during the exposure of an individual field.Subsequently, between consecutive exposure steps, the wafer 30 isconsecutively moved with the wafer stage assembly 20 perpendicularly tothe optical axis of the optical assembly 16 so that the next field ofthe wafer 30 is brought into position relative to the optical assembly16 and the reticle 28 for exposure. Following this process, the imageson the reticle 28 are sequentially exposed onto the fields of the wafer30, and then the next field of the wafer 30 is brought into positionrelative to the optical assembly 16 and the reticle 28.

However, the use of the exposure apparatus 10 provided herein is notlimited to a photolithography system for semiconductor manufacturing.The exposure apparatus 10, for example, can be used as an LCDphotolithography system that exposes a liquid crystal display devicepattern onto a rectangular glass plate or a photolithography system formanufacturing a thin film magnetic head.

The apparatus frame 12 supports the components of the exposure apparatus10. The apparatus frame 12 illustrated in FIG. 1 supports the reticlestage assembly 18, the wafer stage assembly 20, the optical assembly 16and the illumination system 14 above the mounting base 32.

The illumination system 14 includes an illumination source 34 and anillumination optical assembly 36. The illumination source 34 emits abeam (irradiation) of light energy. The illumination optical assembly 36guides the beam of light energy from the illumination source 34 to theoptical assembly 16. The beam illuminates selectively different portionsof the reticle 28 and exposes the wafer 30. In FIG. 1, the illuminationsource 34 is illustrated as being supported above the reticle stageassembly 18. Typically, however, the illumination source 34 is securedto one of the sides of the apparatus frame 12 and the energy beam fromthe illumination source 34 is directed to above the reticle stageassembly 18 with the illumination optical assembly 36.

The illumination source 34 can be a g-line source (436 nm), an i-linesource (365 nm), a KrF excimer laser (248 nm), an ArF excimer laser (193nm) or a F₂ laser (157 nm). Alternatively, the illumination source 34can generate charged particle beams such as an x-ray or an electronbeam. For instance, in the case where an electron beam is used,thermionic emission type lanthanum hexaboride (LaB₆) or tantalum (Ta)can be used as a cathode for an electron gun. Furthermore, in the casewhere an electron beam is used, the structure could be such that eithera mask is used or a pattern can be directly formed on a substratewithout the use of a mask.

The optical assembly 16 projects and/or focuses the light passingthrough the reticle 28 to the wafer 30. Depending upon the design of theexposure apparatus 10, the optical assembly 16 can magnify or reduce theimage illuminated on the reticle 28. The optical assembly 16 need not belimited to a reduction system. It also could be a 1× or magnificationsystem.

When far ultra-violet rays such as the excimer laser is used, glassmaterials such as quartz and fluorite that transmit far ultra-violetrays can be used in the optical assembly 16. When the F₂ type laser orx-ray is used, the optical assembly 16 can be either catadioptric orrefractive (a reticle should also preferably be a reflective type), andwhen an electron beam is used, electron optics can consist of electronlenses and deflectors. The optical path for the electron beams should bein a vacuum.

Also, with an exposure device that employs vacuum ultra-violet radiation(VUV) of wavelength 200 nm or lower, use of the catadioptric typeoptical system can be considered. Examples of the catadioptric type ofoptical system include Japanese Laid-Open Patent Application PublicationNo. 8-171054 and its counterpart U.S. Pat. No. 5,668,672, as well asJapanese Laid-Open Patent Application Publication No. 10-20195 and itscounterpart U.S. Pat. No. 5,835,275. In these cases, the reflectingoptical device can be a catadioptric optical system incorporating a beamsplitter and concave mirror. Japanese Laid-Open Patent ApplicationPublication No. 8-334695 and its counterpart U.S. Pat. No. 5,689,377 aswell as Japanese Laid-Open Patent Application Publication No. 10-3039and its counterpart U.S. patent application Ser. No. 873,605(Application Date: Jun. 12, 1997) also use a reflecting-refracting typeof optical system incorporating a concave mirror, etc., but without abeam splitter, and can also be employed with this invention. Thedisclosures of the above-mentioned U.S. patents and Japanese Laid-Openpatent applications publications are incorporated herein by reference intheir entireties.

In one embodiment, the optical assembly 16 is secured to the apparatusframe 12 with one or more optical mount isolators 37. The optical mountisolators 37 inhibit vibration of the apparatus frame 12 from causingvibration to the optical assembly 16. Each optical mount isolator 37 caninclude a pneumatic cylinder (not shown) that isolates vibration and anactuator (not shown) that isolates vibration and controls the positionwith at least two degrees of motion. Suitable optical mount isolators 37are sold by Integrated Dynamics Engineering, located in Woburn, Mass.For ease of illustration, two spaced apart optical mount isolators 37are shown as being used to secure the optical assembly 16 to theapparatus frame 12. However, for example, three spaced apart opticalmount isolators 37 can be used to kinematically secure the opticalassembly 16 to the apparatus frame 12.

The reticle stage assembly 18 holds and positions the reticle 28relative to the optical assembly 16 and the wafer 30. In one embodiment,the reticle stage assembly 18 includes a reticle stage 38 that retainsthe reticle 28 and a reticle stage mover assembly 40 that moves andpositions the reticle stage 38 and reticle 28.

Somewhat similarly, the device stage assembly 20 holds and positions thewafer 30 with respect to the projected image of the illuminated portionsof the reticle 28. In one embodiment, the device stage assembly 20includes a device stage 42 that retains the wafer 30, a device stagebase 43 that supports and guides the device stage 42, and a device stagemover assembly 44 that moves and positions the device stage 42 and thewafer 30 relative to the optical assembly 16 and the device stage base43. The device stage 42 is described in more detail below.

Each stage mover assembly 40, 44 can move the respective stage 38, 42with three degrees of freedom, less than three degrees of freedom, ormore than three degrees of freedom. For example, in alternativeembodiments, each stage mover assembly 40, 44 can move the respectivestage 38, 42 with one, two, three, four, five or six degrees of freedom.The reticle stage mover assembly 40 and the device stage mover assembly44 can each include one or more movers, such as rotary motors, voicecoil motors, linear motors utilizing a Lorentz force to generate driveforce, electromagnetic movers, planar motors, or other force movers.

In photolithography systems, when linear motors (see U.S. Pat. Nos.5,623,853 or 5,528,118) are used in the wafer stage assembly or thereticle stage assembly, the linear motors can be either an airlevitation type employing air bearings or a magnetic levitation typeusing Lorentz force or reactance force. Additionally, the stage couldmove along a guide, or it could be a guideless type stage that uses noguide. The disclosures of U.S. Pat. Nos. 5,623,853 and 5,528,118 areincorporated herein by reference in their entireties.

Alternatively, one of the stages could be driven by a planar motor thatdrives the stage by an electromagnetic force generated by a magnet unithaving two-dimensionally arranged magnets and an armature coil unithaving two-dimensionally arranged coils in facing positions. With thistype of driving system, either the magnet unit or the armature coil unitis connected to the stage base and the other unit is mounted on themoving plane side of the stage.

Movement of the stages as described above generates reaction forces thatcan affect performance of the photolithography system. Reaction forcesgenerated by the wafer (substrate) stage motion can be mechanicallytransferred to the floor (ground) by use of a frame member as describedin U.S. Pat. No. 5,528,100 and Japanese Laid-Open Patent ApplicationPublication No. 8-136475. Additionally, reaction forces generated by thereticle (mask) stage motion can be mechanically transferred to the floor(ground) by use of a frame member as described in U.S. Pat. No.5,874,820 and Japanese Laid-Open Patent Application Publication No.8-330224. The disclosures of U.S. Pat. Nos. 5,528,100 and 5,874,820 andJapanese Laid-Open Patent Application Publication Nos. 8-135475 and8-330224 are incorporated herein by reference in their entireties.

The measurement system 22 monitors movement of the reticle 28 and thewafer 30 relative to the optical assembly 16 or some other reference.With this information, the control system 24 can control the reticlestage assembly 18 to precisely position the reticle 28 and the devicestage assembly 20 to precisely position the wafer 30. The design of themeasurement system 22 can vary. For example, the measurement system 22can utilize multiple laser interferometers, encoders, mirrors, and/orother measuring devices.

The control system 24 receives information from the measurement system22 and controls the stage mover assemblies 40, 44 to precisely positionthe reticle 28 and the wafer 30. Additionally, the control system 24 cancontrol the operation of the components of the environmental system 26.The control system 24 can include one or more processors and circuits.

The environmental system 26 controls the environment in a gap 246(illustrated in FIG. 2B) between the optical assembly 16 and the wafer30. The gap 246 includes an imaging field. The imaging field includesthe area adjacent to the region of the wafer 30 that is being exposedand the area in which the beam of light energy travels between theoptical assembly 16 and the wafer 30. With this design, theenvironmental system 26 can control the environment in the imagingfield.

The desired environment created and/or controlled in the gap 246 by theenvironmental system 26 can vary accordingly to the wafer 30 and thedesign of the rest of the components of the exposure apparatus 10,including the illumination system 14. For example, the desiredcontrolled environment can be a fluid such as water. Alternatively, thedesired controlled environment can be another type of fluid.

FIG. 2A is a perspective view of the wafer 30, and a portion of theexposure apparatus 10 of FIG. 1 including the optical assembly 16, thedevice stage 42, and the environmental system 26.

FIG. 2B is a cut-away view of the portion of the exposure apparatus 10of FIG. 2A, including the optical assembly 16, the device stage 42, andthe environmental system 26. FIG. 2B illustrates that the opticalassembly 16 includes an optical housing 250A, a last optical element250B, and an element retainer 250C that secures the last optical element250B to the optical housing 250A. Additionally, FIG. 2B illustrates thegap 246 between the last optical element 250B and the wafer 30. In oneembodiment, the gap 246 is approximately I mm.

In one embodiment, the environmental system 26 fills the imaging fieldand the rest of the gap 246 with an immersion fluid 248 (illustrated ascircles). The design of the environmental system 26 and the componentsof the environmental system 26 can be varied. In the embodimentillustrated in FIG. 2B, the environmental system 26 includes animmersion fluid system 252, a fluid barrier 254, and a transport region256. In this embodiment, (i) the immersion fluid system 252 deliversand/or injects the immersion fluid 248 into the gap 246, removes theimmersion fluid 248 from or near the transport region 256, and/orfacilitates the movement of the immersion fluid 248 through thetransport region 256, (ii) the fluid barrier 254 inhibits the flow ofthe immersion fluid 248 away from near the gap 246, and (iii) thetransport region 256 transfers and/or conveys the immersion fluid 248flowing from the gap 246. The fluid barrier 254 also forms a chamber 257near the gap 246.

The design of the immersion fluid system 252 can vary. For example, theimmersion fluid system 252 can inject the immersion fluid 248 at one ormore locations at or near the gap 246 and chamber 257, the edge of theoptical assembly 16, and/or directly between the optical assembly 16 andthe wafer 30. Further, the immersion fluid system 252 can assist inremoving and/or scavenging the immersion fluid 248 at one or morelocations at or near the device 30, the gap 246 and/or the edge of theoptical assembly 16.

In the embodiment illustrated in FIG. 2B, the immersion fluid system 252includes one or more injector nozzles 258 (only one is illustrated)positioned near the perimeter of the optical assembly 16 and animmersion fluid source 260. FIG. 2C illustrates one injector nozzle 258in more detail. In this embodiment, each of the injector nozzles 258includes a nozzle outlet 262 that is in fluid communication with theimmersion fluid source 260. At the appropriate time, the immersion fluidsource 260 provides immersion fluid 248 to the one or more nozzleoutlets 262 that is released into the chamber 257.

FIGS. 2B and 2C also illustrate that the immersion fluid 248 in thechamber 257 sits on top of the wafer 30. The immersion fluid 248 flowsinto the gap 246. Further, as the wafer 30 moves under the opticalassembly 16, it will drag the immersion fluid 248 in the vicinity of thetop surface of the wafer 30 with the wafer 30 into the gap 246.

In one embodiment, the fluid barrier 254 forms the chamber 257 aroundthe gap 246, restricts the flow of the immersion fluid 248 from the gap246, assists in maintaining the gap 246 full of the immersion fluid 248,and facilitates the recovery of the immersion fluid 248 that escapesfrom the gap 246. In one embodiment, the fluid barrier 254 encircles andis positioned entirely around the gap 246 and the bottom of the opticalassembly 16. Further, in one embodiment, the fluid barrier 254 confinesthe immersion fluid 248 to a region on the wafer 30 and the device stage42 centered on the optical assembly 16. Alternatively, for example, thefluid barrier 254 can be positioned around only a portion of the gap 246or the fluid barrier 254 can be off-center of the optical assembly 16.

In the embodiment illustrated in FIGS. 2B and 2C, the fluid barrier 254includes a containment frame 264, and a frame support 268. In thisembodiment, the containment frame 264 is generally annular ring shapedand encircles the gap 246. Additionally, in this embodiment, thecontainment frame 264 includes a top side 270A, an opposed bottom side270B that faces the wafer 30, an inner side 270C that faces the gap 246,and an outer side 270D. Moreover, in this embodiment, the fluid barrier254 includes a channel 272 for receiving the transport region 256. As anexample, the channel 272 can be annular shaped.

The terms top and bottom are used merely for convenience, and theorientation of the containment frame 264 can be rotated. It should alsobe noted that the containment frame 264 can have another shape. Forexample, the containment frame 264 can be rectangular frame shaped,octagonal frame shaped, oval frame shaped, or another suitable shape.

The frame support 268 connects and supports the containment frame 264 tothe apparatus frame 12, another structure, and/or the optical assembly16, above the wafer 30 and the device stage 42. In one embodiment, theframe support 268 supports all of the weight of the containment frame264. Alternatively, for example, the frame support 268 can support onlya portion of the weight of the containment frame 264. In one embodiment,the frame support 268 can include one or more support assemblies 274.For example, the frame support 268 can include three spaced apartsupport assemblies 274 (only two are illustrated in FIG. 2B). In thisembodiment, each support assembly 274 extends between the opticalassembly 16 and the inner side 270C of the containment frame 264.

In one embodiment, each support assembly 274 is a mount that rigidlysecures the containment frame 264 to the optical assembly 16.Alternatively, for example, each support assembly can be a flexure thatsupports the containment frame 264 in a flexible fashion. As usedherein, the term “flexure” shall mean a part that has relatively highstiffness in some directions and relatively low stiffness in otherdirections. In one embodiment, the flexures cooperate (i) to berelatively stiff along the X axis and along the Y axis, and (ii) to berelatively flexible along the Z axis. In this embodiment, the flexurescan allow for motion of the containment frame 264 along the Z axis andinhibit motion of the containment frame 264 along the X axis and the Yaxis.

Alternatively, for example, each support assembly 274 can be an actuatorthat can be used to adjust the position of the containment frame 264relative to the wafer 30 and the device stage 42. In this embodiment,the frame support 268 can also include a frame measurement system (notshown) that monitors the position of the containment frame 264. Forexample, the frame measurement system can monitor the position of thecontainment frame 264 along the Z axis, about the X axis, and/or aboutthe Y axis. With this information, the support assemblies 274 can beused to adjust the position of the containment frame 264. In thisembodiment, the support assemblies 274 can actively adjust the positionof the containment frame 264.

FIGS. 2B and 2C also illustrate the transport region 256 in more detail.In this embodiment, the transport region 256 is a substrate 275 that issubstantially annular disk shaped, encircles the gap 246, and issubstantially concentric with the optical assembly 16. Alternatively,for example, the substrate 275 can be another shape, including ovalframe shaped, rectangular frame shaped or octagonal frame shaped. Stillalternatively, for example, the transport region 256 can include aplurality of substrate segments that cooperate to encircle a portion ofthe gap 246, and/or a plurality of substantially concentric substrates.

The dimensions of the transport region 256 can be selected to achievethe desired immersion fluid recovery rate.

Further, in this embodiment, the transport region 256 is secured to thecontainment frame 264 at or near the bottom side 270B of the containmentframe 264 and cooperates with the containment frame 264 to form aremoval chamber 276 next to and above the transport region 256.Moreover, as illustrated in FIG. 2C, the transport region 256 includes afirst surface 278A that is adjacent to the removal chamber 276 and anopposite second surface 278B that is adjacent to the device 30 and thegap 246.

In this embodiment, the transport region 256 captures, retains, and/orabsorbs at least a portion of the immersion fluid 248 that flows betweenthe containment frame 264 and the wafer 30 and/or the device stage 42.The type of material utilized in the transport region 256 can vary. Inone embodiment, the substrate 275 includes a plurality of passages 280.For example, the passages 280 can be relatively small and tightlypacked.

As an example, the transport region 256 can be a porous material havinga plurality of pores and/or interstices that convey the immersion fluid248 by capillary action. In this embodiment, the passages 280 can besmall enough so that capillary forces draw the immersion fluid 248 intothe pores. Examples of suitable materials include wick type structuresmade of metals, glasses, or ceramics. Examples of suitable wick typestructures include any material with a network of interconnected, smallpassages, including, but not limited to, woven fiberglass, sinteredmetal powders, screens, wire meshes, or grooves in any material. Thetransport region 256 can be hydrophilic.

In one embodiment, the transport region 256 has a pore size of betweenapproximately 20 and 200 microns. In alternative embodiments, thetransport region 256 can have a porosity of at least approximately 40,80, 100, 140, 160 or 180.

In certain embodiments, a relatively higher flow capacity is required.To accommodate higher flow, larger porosity material may be necessaryfor the transport region 256. The choice for the porosity of thetransport region 256 depends on the overall flow rate requirement of thetransport region 256. Larger overall flow rates can be achieved by usinga transport region 256 having a larger porosity, decreasing thethickness of the transport region 256, or increasing the surface area ofthe transport region 256. In one embodiment, with a flow raterequirement of 0.3-1.0 L/min in immersion lithography, pores size of40-150 μm can be used to cover a 30-150 cm² area for immersion fluid 248recovery. The type and specifications of the porous material alsodepends on the application and the properties of the immersion fluid248.

Referring back to FIG. 2B, in certain embodiments, the transport region256 has a limited capacity to absorb the immersion fluid 248. In oneembodiment, the immersion fluid system 252 includes a fluid removalsystem 282 that removes immersion fluid 248 from or near the transportregion 256 and that is in fluid communication with the transport region256 and the removal chamber 276. With this design, the immersion fluid248 can be captured with the transport region 256 and removed by thefluid removal system 276.

In one embodiment, the fluid removal system 282 removes the immersionfluid 248 from the top first surface 278A of the transport region 256allowing additional immersion fluid 248 to flow into the bottom, secondsurface 278B of the transport region 256. For example, the fluid removalsystem 282 can create a pressure differential across the transportregion 256. In one example, the fluid removal system 282 causes thepressure at the first surface 278A to be lower than the pressure at thesecond surface 278B.

The removal of the immersion fluid 248 can be accomplished in severaldifferent ways and a number of embodiments of the fluid removal system282 are described below.

FIG. 2C illustrates that a frame gap 284 exists between (i) the bottomside 270B of the containment frame 264 and the second surface 278B ofthe transport region 256, and (ii) the wafer 30 and/or the device stage42 to allow for ease of movement of the device stage 42 and the wafer 30relative to the containment frame 264. The size of the frame gap 284 canvary. In one embodiment, the frame gap 284 is between approximately 0.1and 2 mm. In alternative examples, the frame gap 284 can beapproximately 0.05, 0.1, 0.2, 0.5, 1, 1.5, 2, 3, or 5 mm.

With this embodiment, most of the immersion fluid 248 is confined withinthe fluid barrier 254 and most of the leakage around the periphery isscavenged within the narrow frame gap 284 by the transport region 256.In this case, when the immersion fluid 248 touches the transport region256, it is drawn into the transport region 256 and absorbed. Thus, thetransport region 256 inhibits any immersion fluid 248 from flowingoutside the ring.

FIG. 2D illustrates a cut-away view of a portion of another embodimentof an exposure apparatus 10D that is somewhat similar to the embodimentillustrated in FIG. 2C. However, in FIG. 2D, the device 30D and/or thestage 42D is closer to the bottom side 270BD of the inner side 270CDand/or the outer side 270DD of the containment frame 264D than thesecond surface 278DB of the transport region 256D. Stated another way,the distance between the bottom side 270BD and the device 30D and/or thestage 42D is less than the distance between the second surface 278DB andthe device 30D and/or the stage 42D.

FIG. 3A illustrates one embodiment of the immersion fluid source 260. Inthis embodiment, the immersion fluid source 260 includes (i) a fluidreservoir 386A that retains the immersion fluid 248, (ii) a filter 386Bin fluid communication with the fluid reservoir 386A that filters theimmersion fluid 248, (iii) a de-aerator 386C in fluid communication withthe filter 386B that removes any air, contaminants, or gas from theimmersion fluid 248, (iv) a temperature controller 386D, e.g., a heatexchanger or chiller, in fluid communication with the de-aerator 386Cthat controls the temperature of the immersion fluid 248, (v) a pressuresource 386E, e.g., a pump, in fluid communication with the temperaturecontroller 386D, and (vi) a flow controller 386F that has an inlet influid communication with the pressure source 386E and an outlet in fluidcommunication with the nozzle outlets 262 (illustrated in FIG. 2C), theflow controller 386F controlling the pressure and flow to the nozzleoutlets 262.

Additionally, the immersion fluid source 260 can include (i) a pressuresensor 386G that measures the pressure of the immersion fluid 248 thatis delivered to the nozzle outlets 262, (ii) a flow sensor 386H thatmeasures the rate of flow of the immersion fluid 248 to the nozzleoutlets 262, and (iii) a temperature sensor 386I that measures thetemperature of the immersion fluid 248 to the nozzle outlets 262. Theoperation of these components can be controlled by the control system 24(illustrated in FIG. 1) to control the flow rate, temperature and/orpressure of the immersion fluid 248 to the nozzle outlets 262. Theinformation from these sensors 386G-3861 can be transferred to thecontrol system 24 so that the control system 24 can appropriately adjustthe other components of the immersion fluid source 260 to achieve thedesired temperature, flow and/or pressure of the immersion fluid 248.

The orientation of the components of the immersion fluid source 260 canbe varied. Further, one or more of the components may not be necessaryand/or some of the components can be duplicated. For example, theimmersion fluid source 260 can include multiple pumps, multiplereservoirs, temperature controllers or other components. Moreover, theenvironmental system 26 can include multiple immersion fluid sources260.

The rate at which the immersion fluid 248 is pumped into the gap 246(illustrated in FIG. 2B) can vary. In one embodiment, the immersionfluid 248 is supplied to the gap 246 via the nozzle outlets 262 at arate of between approximately 0.5 liters/min to 2 liters/min. However,the rate can be greater or less than these amounts.

The type of immersion fluid 248 can be varied to suit the designrequirements of the apparatus 10. In one embodiment, the immersion fluid248 is a fluid such as de-gassed, de-ionized water. Alternatively, forexample, the immersion fluid 248 can be another type of fluid, such as aper-fluorinated polyether (PFPE) such as Fomblin oil.

FIG. 3B illustrates a first embodiment of the fluid removal system 382Band an illustration of a portion of the fluid barrier 254, the transportregion 256, the wafer 30, and the immersion fluid 248. The fluid removalsystem 382B is also referred to herein as a pressure system. In oneembodiment, the fluid removal system 382B creates and/or applies atransport pressure to the first surface 278A of the transport region256. In this embodiment, the fluid removal system 382B maintains thetransport pressure at the first surface 278A of the transport region 256so that a pressure differential exists between the first surface 278Aand the second surface 278B. In alternative embodiments, the fluidremoval system 382B controls the pressure in the removal chamber 276 sothat the transport pressure at the first surface 278A is approximately−10, −100, −500, −1000, −2000, −5000, −7000 or −10,000 Pa gage.

In FIG. 3B, the fluid removal system 382B includes (i) a low pressuresource 390BA that creates a low chamber pressure in the removal chamber276, and (ii) a recovery reservoir 390BC that captures immersion fluid248 from the removal chamber 276. In this embodiment, the low pressuresource 390BA can include a pump or vacuum source 390BD, and a chamberpressure regulator 390BE for precisely controlling the chamber pressurein the chamber 276. In alternative embodiments, for example, the chamberpressure is controlled to be approximately −10, −100, −500, −1000,−2000, −5000, −7000 or −10,000 Pa gage. The chamber pressure regulator390BE can be controlled by the control system 24 to control the chamberpressure.

FIG. 3C illustrates another embodiment of the fluid removal system 382Cand an illustration of a portion of the fluid barrier 254, the transportregion 256, the wafer 30, and the immersion fluid 248. In thisembodiment, the fluid removal system 382C forces a dry removal fluid 396(illustrated as triangles), e.g., air through the removal chamber 276and across the top first surface 278A of the transport region 256. Theremoval fluid 396 will dry the top surface 278A of the transport region256, pumping immersion fluid 248 out of the transport region 256. Theremoval fluid 396 can be heated in some cases, improving the flow of theimmersion fluid 248 into the dry removal fluid 396. Stated another way,in one embodiment, the removal fluid 396 is at a removal fluidtemperature that is higher than an immersion fluid temperature of theimmersion fluid 248.

In FIG. 3C, the fluid removal system 382C includes (i) a fluid source396A of the pressurized drying removal fluid 396, (ii) a temperaturecontroller 396B that controls the temperature of the drying removalfluid 396, (iii) a flow sensor 396C that measures the flow of the dryingremoval fluid 396, and (iv) a temperature sensor 396D that measures thetemperature of the drying removal fluid 396. The fluid source 396A caninclude a pump controlled by the control system 24, and the temperaturecontroller 396B can be a heater that is controlled by the control system24.

FIG. 3D illustrates yet another embodiment of the fluid removal system382D and an illustration of a portion of the fluid barrier 254, thetransport region 256, the wafer 30, and the immersion fluid 248. In thisembodiment, the transport region 256 is extended outside the fluidbarrier 254. Further, the fluid removal system 382C includes a heatsource 397 that directs a heated fluid 396F (illustrated as triangles)at the first surface 278A of the transport region 256, causing theimmersion fluid 248 to boil out of the transport region 256 and becaptured.

The orientation of the components of the fluid removal systems 382B-382Dillustrated in FIGS. 3B-3D can be varied. Further, one or more of thecomponents may not be necessary and/or some of the components can beduplicated. For example, each of the fluid removal systems 382B, 382C,382D can include multiple pumps, multiple reservoirs, valves, or othercomponents. Moreover, the environmental system 26 can include multiplefluid removal systems 382B, 382C, 382D.

FIG. 4 is an enlarged view of a portion of another embodiment of theenvironmental system 426, a portion of the wafer 30, and a portion ofthe device stage 42. In this embodiment, the environmental system 426 issomewhat similar to the corresponding component described above andillustrated in FIGS. 2A-2C. However, in this embodiment, the transportregion 456 is slightly different. In particular, in this embodiment, thepassages 480 (only two are illustrated) in the substrate 475 of thetransport region 456 are a plurality of spaced apart transport aperturesthat extend substantially transversely through the substrate 475 betweenthe first surface 478A and the second surface 478B.

In this embodiment, for example, the substrate 475 can be made of amaterial such as glass or other hydrophilic materials. In oneembodiment, the transport apertures 480 can have a diameter of betweenapproximately 0.1 and 0.2 mm. However, in certain embodiments, thetransport apertures can be larger or smaller than these amounts.

With this design, for example, one or more of the fluid removal systems382B, 382C (illustrated in FIGS. 3B and 3C) can be used to apply avacuum or partial vacuum on the transport apertures 480. The partialvacuum draws the immersion fluid 248 through the transport region 456.

FIG. 5A is a cut-away view of a portion of another embodiment of theexposure apparatus 510, including the optical assembly 516, the devicestage 542, and the environmental system 526. FIG. 5A also illustratesthe wafer 30, the gap 546, and that the immersion fluid 548 fills thegap 546. FIG. 5B illustrates an enlarged portion of FIG. 5A taken online 5B-5B.

In this embodiment, the environmental system 526 again includes animmersion fluid system 552, a fluid barrier 554, and a transport region556 that are somewhat similar to the corresponding components describedabove. In this embodiment, the fluid barrier 554 includes a containmentframe 564 that forms a chamber 557 around the gap 546, and a framesupport 568 that connects and supports the containment frame 564 to theapparatus frame 12. However, in this embodiment, the containment frame564 includes (i) an annular shaped first channel 581 that defines anozzle outlet 562 that is in fluid communication with an immersion fluidsource 560 of the immersion fluid system 552; (ii) an annular shapedsecond channel 583, (iii) an annular shaped third channel 585, and (iv)an annular shaped fourth channel 587 for receiving the transport region556. In this embodiment, the channels 581, 583, 585, 587 areapproximately concentric and are centered about the optical assembly516. Further, in this embodiment, the second channel 583 encircles thefirst channel 581, the third channel 585 encircles the second channel583, and the fourth channel 587 encircles the third channel 585.However, the shape, orientation, and/or position of the channels 581,583, 585, 587 can be changed.

In one embodiment, the immersion fluid system 552 provides the immersionfluid 548 to the first channel 581 and the nozzle outlet 562 that isreleased into the chamber 557. The transport region 556 cooperates withthe containment frame 564 to form a removal chamber 576 next to andabove the transport region 556. Moreover, the transport region 556includes a first surface 578A that is adjacent to the removal chamber576 and an opposite second surface 578B that is adjacent to the device30 and the gap 546.

In this embodiment, the third channel 585 is in fluid communication witha first removal system 528A. In one embodiment, the first removal system528A creates a vacuum or partial vacuum in the third channel 585 thatpulls and/or draws the immersion fluid 548 into the third channel 585.For example, in alternative embodiments, the first removal system 528Acan maintain the pressure in the third channel 585 at approximately −10,−100, −500, −1000, −2000, −5000, −7000 or −10,000 Pa gage.

Further, in this embodiment, the fourth channel 587 is in fluidcommunication with a second removal system 528B. In this embodiment, thesecond removal system 528B removes the immersion fluid 548 from the topfirst surface 578A of the transport region 556, allowing additionalimmersion fluid 548 to flow into the bottom, second surface 578B of thetransport region 556.

In one embodiment, the design of the first removal system 528A can besomewhat similar to the design of one of the removal systems 382B, 382Cillustrated in FIGS. 3B-3D and/or the design of the second removalsystem 528B can be somewhat similar to one of the designs illustrated inFIGS. 3B-3D.

In one embodiment, the majority of the immersion fluid 548 exiting fromthe gap 546 is recovered through the third channel 585. For example, thethird channel 585 can recover between approximately 80-90 percent of theimmersion fluid 548 recovered from the gap 546. In alternativeembodiments, the third channel 585 can recover at least approximately50, 60, 70, 80, or 90 percent of the immersion fluid 548 recovered fromthe gap 546. With this design, the fourth channel 587 can be used tocapture the immersion fluid 548 not captured by the third channel 585.

Additionally, in one embodiment, the environmental system 526 includes apressure controller 591 that can be used to control the pressure in thegap 546. In one embodiment, the pressure controller 591 can cause thepressure in the gap 546 to be approximately equal to the pressureoutside of the gap 546. For example, in one embodiment, the secondchannel 583 defines the pressure controller 591. In this embodiment, thesecond channel 583 is open to the atmospheric pressure and is positionedinside the periphery of third channel 585. With this design, thenegative pressure (vacuum or partial vacuum) in the third channel 585will not strongly influence the pressure between the optical assembly516 and the wafer 30.

Alternatively, for example, a control pressure source 593 can deliver acontrol fluid 595 (illustrated as triangles) to the second channel 583that is released into the gap 546. In one embodiment, the control fluid595 can be a gas that is not easily absorbed by the immersion fluid 548.For example, if the immersion fluid 548 is water, the control fluid 595can be water. If the immersion fluid 548 does not absorb the controlfluid 595 or otherwise react to it, the chances of bubble formation onthe surface of the wafer 30 can be reduced.

In yet another embodiment, the environmental system 526 can include adevice for creating a fluid bearing (not shown) between the containmentframe 564 and the wafer 30 and/or the device stage 542. For example, thecontainment frame 564 can include one or more bearing outlets (notshown) that are in fluid communication with a bearing fluid source (notshown) of a bearing fluid (not shown). In this embodiment, the bearingfluid source provides pressurized fluid to the bearing outlet to createthe aerostatic bearing. The fluid bearings can support all or a portionof the weight of the containment frame 564.

It should be noted that in each embodiment, additional transport regionscan be added as necessary.

Semiconductor devices can be fabricated using the above describedsystems, by the process shown generally in FIG. 6A. In step 601 thedevice's function and performance characteristics are designed. Next, instep 602, a mask (reticle) having a pattern is designed according to theprevious designing step, and in a parallel step 603 a wafer is made froma silicon material. The mask pattern designed in step 602 is exposedonto the wafer from step 603 in step 604 by a photolithography systemdescribed hereinabove in accordance with the invention. In step 605 thesemiconductor device is assembled (including the dicing process, bondingprocess and packaging process). Finally, the device is then inspected instep 606.

FIG. 6B illustrates a detailed flowchart example of the above-mentionedstep 604 in the case of fabricating semiconductor devices. In FIG. 6B,in step 611 (oxidation step), the wafer surface is oxidized. In step 612(CVD step), an insulation film is formed on the wafer surface. In step613 (electrode formation step), electrodes are formed on the wafer byvapor deposition. In step 614 (ion implantation step), ions areimplanted in the wafer. The above mentioned steps 611-614 form thepreprocessing steps for wafers during wafer processing, and selection ismade at each step according to processing requirements.

At each stage of wafer processing, when the above-mentionedpreprocessing steps have been completed, the following post-processingsteps are implemented. During post-processing, first, in step 615(photoresist formation step), photoresist is applied to a wafer. Next,in step 616 (exposure step), the above-mentioned exposure device is usedto transfer the circuit pattern of a mask (reticle) to a wafer. Then instep 617 (developing step), the exposed wafer is developed, and in step618 (etching step), parts other than residual photoresist (exposedmaterial surface) are removed by etching. In step 619 (photoresistremoval step), unnecessary photoresist remaining after etching isremoved.

Multiple circuit patterns are formed by repetition of thesepreprocessing and post-processing steps.

While the particular exposure apparatus 10 as shown and described hereinis fully capable of obtaining the objects and providing the advantagespreviously stated, it is to be understood that it is merely illustrativeof embodiments of the invention. No limitations are intended to thedetails of construction or design herein shown.

1. A lithographic projection apparatus arranged to project a patternfrom a patterning device onto a substrate using a projection system andhaving a liquid supply system arranged to supply a liquid to a spacebetween the projection system and the substrate, comprising a liquidremoval system including: a conduit having an open end adjacent a volumein which liquid will be present; a porous member between the end of theconduit and the volume; and a suction device arranged to create apressure differential across the porous member.
 2. The apparatusaccording to claim 1, wherein the liquid removal system is arranged toremove liquid from a volume adjacent the space.
 3. The apparatusaccording to claim 2, further comprising a member at least partiallysurrounding the space and wherein the conduit comprises a recess in asurface of the member facing the substrate, the porous member closingthe recess.
 4. The apparatus according to claim 3, wherein the memberforms a closed loop around the space and the recess extends around thewhole of the member.
 5. The apparatus according to claim 3, wherein themember further comprises a gas supply circuit having an outlet in asurface facing the substrate.
 6. The apparatus according to claim 5,wherein the member further comprises a fluid extraction circuit havingan inlet located between the recess and the outlet.
 7. The apparatusaccording to claim 5, wherein the member further comprises a fluidextraction circuit having an inlet located radially outwardly of theoutlet.
 8. The apparatus according to claim 3, wherein the memberfurther comprises a fluid supply circuit having an outlet in a surfacefacing the substrate so as to form a fluid bearing to at least partlysupport the weight of the member.
 9. The apparatus according to claim 3,wherein, during use, the member is supported at a height above thesubstrate in the range of from 0.05 mm to 5 mm.
 10. The apparatusaccording to claim 1, further comprising a member at least partiallysurrounding the space and wherein the conduit comprises a recess in asurface of the member, the porous member closing the recess.
 11. Theapparatus according to claim 1, wherein the liquid removal systemcomprises a vacuum source and the conduit comprises a pipe connected toa liquid collection chamber.
 12. The apparatus according to claim 1,wherein the porous member has pores having a diameter in the range offrom 20 to 200 μm.
 13. The apparatus according to claim 1, wherein theporous member is hydrophilic.
 14. A device manufacturing methodcomprising: projecting a patterned beam of radiation through a liquidonto a substrate using a projection system; and removing liquid from avolume by providing a pressure differential across a porous memberbounding at least in part the volume.
 15. The method according to claim14, wherein the volume is adjacent a space comprising the liquid throughwhich the patterned beam is projected.
 16. The method according to claim15, comprising removing the liquid from the volume using a recess in asurface, facing the substrate, of a member at least partiallysurrounding the space, the porous member closing the recess.
 17. Themethod according to claim 16, wherein the member forms a closed looparound the space and the recess extends around the whole of the member.18. The method according to claim 16, further comprising supplying gasfrom a surface facing the substrate.
 19. The method according to claim18, further comprising removing fluid from a position between the recessand the position where the gas is being supplied.
 20. The methodaccording to claim 18, further comprising removing fluid from a positionlocated radially outwardly of the position where the gas is beingsupplied.
 21. The method according to claim 16, further comprisingsupplying fluid from a surface facing the substrate so as to form afluid bearing to at least partly support the weight of the member. 22.The method according to claim 16, comprising supporting the member at aheight above the substrate in the range of from 0.05 mm to 5 mm.
 23. Themethod according to claim 14, comprising removing the liquid from thevolume using a recess in a surface of a member at least partiallysurrounding the space, the porous member closing the recess.
 24. Themethod according to claim 14, comprising removing the liquid from thevolume through a conduit connected to a liquid collection chamber.